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Agreements to limit emissions of greenhouse gases are currently the focus of international negotiations, and with such accords will come the need to accurately estimate these emissions, monitor their changes over time, and verify them with independent data. In that context, the National Research Council convened a committee of experts to assess current capabilities for estimating and verifying greenhouse gas emissions and to identify ways to improve these capabilities. The committee examined the greenhouse gases that result from human activities and that are long-lived in the atmosphere, particularly carbon dioxide, which is the single largest contributor to global climate change. It found that countries can estimate their carbon dioxide emissions from fossil-fuel use accurately enough to support monitoring, but currently there is no sufficiently accurate way to verify countries' self-reported estimates using independent data, such as atmospheric measurements. Strategic investments could be made that within five years would both improve self-reporting and yield a capability to verify these estimates, reducing uncertainties about emissions of carbon dioxide from fossil-fuel use and deforestation -- responsible for three-quarters of emissions of gases likely covered by an international agreement -- to less than 10 percent.

Key Messages

Current methods produce emissions estimates with unacceptably high uncertainties

Independent estimates of carbon dioxide emissions could be improved through research to reach a better understanding of emissions in the atmosphere

Independent estimates of fluxes from land-use sources and sinks could be improved by producing a global map of land use and land cover change at least every two years, using Landsat and high-resolution satellite imagery

National inventories of greenhouse gas emissions could be strengthened by extending more rigorous reporting and review requirements to all countries, not just developed countries

Strategic investments focused on the most important sources of greenhouse gases, the highest emitting countries, and the most abundant and longest-lived gases, could yield improvements in monitoring and verification within 5 years

The NASA Orbiting Carbon Observatory, which failed on launch in February 2009, would have been a useful tool to independently estimate carbon dioxide emissions -- NASA should build and launch a replacement

The international atmospheric sampling network should be extended to research greenhouse gas emissions over a representative sample of large local emitters, such as cities and power plants, and to fill in underrepresented regions globally